The present invention relates to heat exchange devices and more particularly to a header structure for use with a multiple tube heat transfer or heat exchange apparatus.
In my U.S. Pat. No. 3,651,551, I provide a method of assembling a heat transfer apparatus utilizing a header structure that requires flanges, gaskets, nuts, bolts and a multitude of machine and fitted parts in order to complete a working unit. Although the finished and assembled header structure functions satisfactorily, it is a relatively costly item to produce. The primary object of the design disclosed in my above referenced patent was to provide a header structure that could be readily disassembled for inspection and cleaning when used in a sanitary operation such as in the conveying of milk or milk products.
In the past few years, sanitarians have recognized that a properly designed and completely constructed tubular heat exchanger can be cleaned and sanitized in the assembled condition thus eliminating the need to disassemble the component parts for manual washing and to dispense with the requirement that the interior surfaces of the heat exchanger be available for inspection. It has been established that an all welded tubular heat exchanger can be efficiently and effectively cleaned by circulating, washing and sanitizing solutions through the interior areas at fairly high velocities (7 ft. per second and up). This system, known as a CIP or "cleaned in place" system, is widely accepted in the milk processing industry as being highly superior to the former method of disassembly and hand or manual washing of processing equipment parts.
There are certain critical features that must be incorporated into the design of a tubular heat exchanger in order to provide a unit of processing equipment that will be considered suitable for cleaning in place. These features, set forth in the 3-A SANITARY STANDARDS FOR TUBULAR HEAT EXCHANGERS FOR MILK AND MILK PRODUCTS formulated jointly by the International Association of Milk, Food and Environmental Sanitarians, the United States Public Health Service and the Dairy Industry Committee include the following:
1. Self-draining of the product channel or channels. PA0 2. Elimination of pockets and dead ends in the product flow channels. PA0 3. Maintenance of a uniform area throughout the products flow channel in order to maintain a uniform velocity of the cleaning solution through this area during the cleaning cycle. PA0 4. All interior angles of 135.degree. or less, within the product flow area, must have a sanitary radius.
The term "sanitary radius" as defined in the 3-A Standards is a radius of at least 1/32 inch for circular cross-sectional tubing and 150 inch on all non-circular cross-sectional tubing.
The heat exchanger set forth in my previously described patent provides the first three of the requirements set forth above. A principal object of the present invention is to provide an improved header structure for a heat exchange device such as that described in my previous patent which further incorporates the fourth 3-A Sanitary Standards requirement so as to provide a heat exchange apparatus which fully complies with the requirements for a clean in place system.
The above and other beneficial objects and advantages are attained in accordance with the present invention by providing an improved header for a heat transfer apparatus of the type utilizing a plurality of longitudinally extending concentric tubes including an inner tube, an intermediate tube and an outer tube with one end of the intermediate tube extending longitudinally beyond the outer tube and the corresponding end of the inner tube extending longitudinally beyond the end of the intermediate tube. The header includes sealing members for the intermediate and outer tubes. Each sealing member is butt welded at one end of its associated tube. The other end of the sealing members defines an inwardly directed sanitary radius which is welded to an outwardly directed sanitary radius formed in a band which, in turn, is welded to the next innermost tube section. The method of assembling a header in accordance with the above is also provided.